1. Field of the Invention
The present invention relates to a single wafer LPCVD apparatus, and more particularly, to a single wafer LPCVD apparatus which adopts a direct heating technique, thereby enabling hot processing, uniform temperature distribution within a space in a vacuum chamber and plasma processing as well.
2. Description of the Related Art
In general, a batch-type Chemical Vapor Deposition (CVD) has been carried out in order to improve the yield of thin film deposition. In the batch-type CVD, multiple wafers are loaded into a single reaction tube. However, since wafers are closely and vertically arranged in such the batch-type CVD, reaction gases fail to sufficiently contact with some portions of the wafers, which is detrimental to the uniformity of thin film deposition.
In order to solve such a problem, a Low Pressure Chemical Vapor Deposition (LPCVD) was proposed. Different from a conventional Atmospheric Pressure Chemical Vapor Deposition (APCVD) in which a thin film is deposited in the vicinity of the atmospheric pressure, the LPCVD carries out thin film deposition at a pressure ranging from 0.1 to 50 torr. In the LPCVD, a CVD is carried out under a low pressure as set forth above, and thus the mean free path of reaction gases becomes long. Therefore, the reaction gases sufficiently flow through the wafers even in a batch-type LPCVD, thereby improving the uniformity of thin film deposition as well as the step coverage. As a result, contact holes or trenches can be filled without pores.
Therefore, the LPCVD is mainly used in a practical semiconductor device manufacturing process due to the foregoing merits although the film deposition rate thereof is lower than the APCVD.
The recent trend of using larger wafers has replaced the batch-type LPCVD with a single wafer LPCVD in order to further improve the uniformity of film deposition and the step coverage. In the single wafer LPCVD, a single wafer is loaded into the reaction chamber.
FIG. 1 is a schematic view illustrating a conventional single wafer LPCVD apparatus.
Referring to FIG. 1, a vacuum chamber (not shown in the drawing) is covered with a quartz dome 20 and thereby it is sealed. The quartz dome 20 is covered with a bell jar 30. Between the bell jar 30 and the quartz dome 20 is installed a dome-type plasma electrode 40, which is applied with Radio Frequency (RF) power from an RF power supply 50 to generate plasma within the quartz dome 20.
Along the side wall of the bell jar 30 are vertically installed an insulation wall 34 and an adiabatic wall 32 which is placed outer from the insulation wall 34. Between the adiabatic wall 32 and the insulation wall 34 is installed a heater wire 36 wound around the insulation wall 34 in the shape of a coil. The adiabatic wall 32 prevents heat radiated from the heater wire 36 from being transferred to the outside. Current flows through the heater wire 36 during heat generation because the heater wire 36 generates heat by electric resistance. Therefore, the insulation wall 34 is installed to prevent RF noises generated in the dome-type plasma electrode 40 from being transferred to the heater wire 36.
As described above, the conventional single wafer LPCVD apparatus has a vertical overall configuration with the heater wire 36 winding around the side of the quartz dome 20. Therefore, the distance between the heater wire 36 and the quartz dome 20 gradually increases from a shoulder of the quartz dome 20, and there is no heater wire 30 at all over the quartz dome 20. Therefore, the temperature distribution is nonuniform within the vacuum chamber, and the heater wire should be adjusted up to a very high temperature when a hot processing is required. The heater wire capable of stably enduring such a hot processing can be barely prepared, and the cost thereof is very high.
Accordingly, the present invention has been devised to solve the foregoing problems of the prior art, and it is therefore an object of the invention to provide a single wafer LPCVD apparatus which adopts a direct heating technique rather than an indirect heating technique of the prior art, thereby enabling hot processing, uniform temperature distribution within a space in a vacuum chamber and plasma processing as well.
To accomplish the above object and other advantages, there is a single wafer LPCVD apparatus. The apparatus comprises: a vacuum chamber having an upper part sealed by a quartz dome, the vacuum chamber receiving a single wafer loaded therein; a bell jar having a dome-shaped inner wall, covering the quartz dome, and spaced by a selected interval from the quartz dome; a dome-shaped plasma electrode established between the bell jar and the quartz dome; an RF power supply for applying an RF power to the dome-shaped plasma electrode; an adiabatic wall provided on the entire inner wall of the bell jar; a sheath heater having a heater wire and an insulator for covering the heater wire, the sheath heater being attached and established to a surface of the adiabatic wall in a shape of a coil; and a cooling pipe established in a wall of the bell jar.
According to another aspect of the invention, there is a single wafer LPCVD apparatus. The apparatus comprises: a vacuum chamber with an upper part sealed by a quartz dome, the vacuum chamber receiving a single wafer loaded therein; a bell jar having a dome-shaped inner wall, covering the quartz dome, and spaced by a selected interval from the quartz dome; an adiabatic wall provided on the entire inner wall of the bell jar; a sheath heater having a heater wire and an insulator for covering the heater wire, the sheath heater being applied to a surface of the adiabatic wall in a shape of a coil; a metal tube functioning as a plasma electrode and surrounding the nonconductor of the sheath heater; an RF power supply for applying an RF power to the metal tube; and a cooling pipe provided in a wall of the bell jar.